Search

The performance of sustainable polymers can be modified and enhanced by incorporating functional groups in the backbone of the polymer chain that increases intermolecular interactions, thus impacting the thermal properties of the material. However, in-depth studies on the role of intermolecular interactions on the crystallization of these polymers are still needed. This work aims to ascertain whether incorporating functional groups able to induce intermolecular interactions can be used as a suitable systematic strategy to modify the polymer thermal properties and crystallization kinetics. Thus, amide and additional ester groups have been incorporated into aliphatic polyesters (PEs). The impact of intermolecular interactions on the melting and crystallization behavior, crystallization kinetics, and crystalline structure has been determined. Functional groups that form strong intermolecular interactions increase both melting and crystallization temperatures but retard the crystallization kinetics. Selecting appropriate functional groups allows tuning the crystallinity degree, which can potentially improve the mechanical properties and degradability in semicrystalline materials. The results demonstrate that it is possible to tune the thermal transitions and the crystallization kinetics of PEs independently by varying their chemical structure. [ABSTRACT FROM AUTHOR]

We present a collection of hands-on experiments that collectively teach precollege students fundamental concepts of polymer synthesis and characterization. These interactive experiments are performed annually as part of an all-day outreach event for high school students that can inform the development of ongoing polymer education efforts in a university setting. The Advanced Polymer Synthesis experiment aims to introduce broad concepts of polymer synthesis. Techniques such as ring-opening polymerization are explained and demonstrated. The Block Polymer Micellization experiment extends this idea to block polymers for drug delivery applications. Students are taught the idea of self-assembly and prepare micelles to encapsulate ß-carotene in water with flash nanoprecipitation. In terms of materials characterization, the vast physical properties space of polymers is explored. The Happy-Sad Spheres experiment provides an interactive demonstration of the glass transition temperature, while the Polymer Swelling/Rheology experiment features the interesting properties of cross-linked and entangled polymers. Evaluation surveys showed positive feedback from students in learning polymer concepts through this program. Overall, the simple principles taught by these outreach experiments can be easily incorporated into modern laboratory curricula with broad implications for disseminating public knowledge and promoting continued interest in polymer science and engineering.

The origin of melt memory effects associated with semicrystalline polymers and the physical parameters involved in this process have been widely studied in the literature. However, a comprehensive understanding of the role of intermolecular interactions on melt memory is still being developed. For this purpose, we have considered aliphatic polyesters and we have incorporated amide and additional ester groups. Inserting these additional functional groups, the strength of the intermolecular interactions increases widening the melt memory effect. Not only the presence of the functional groups but also the position of these groups in the repeating unit plays a role in the melt memory effect as it impacts the strength of the intermolecular interactions in the crystals. The study of the effect of intermolecular interactions has been extended to successive self-nucleation and annealing thermal fractionation experiments to explore for the first time the role of intermolecular forces on the fractionation capacity of linear polymers. We demonstrated that intermolecular interactions act as intrinsic defects interrupting the crystallizable chain length, thus facilitating thermal fractionation. Overall, this work sheds light on the role of intermolecular interactions on the crystallization behavior of a series of aliphatic polyesters. [ABSTRACT FROM AUTHOR]

The synthesis of nanoporous polymer monoliths is demonstrated with tailored surface chemistry from block copolymers. Polystyrene-polydimethylacrylamide-polyactide (PS - PDMA - PLA) triblock copolymers that self- assemble into a core-shell cylindrical structure is identified and their macroscale alignments are employed to prepare highly oriented nanostructured materials.

The preparation, structural characterization, and detailed lactide polymerization behavior of a new Zn(II) alkoxide complex, (L1ZnOEt)(Sub 2) (L1=2,4-di-tert-butyl-6- {[(2'-dimethylaminoethyl)methylamino]-methyl}phenolate) is reported. The effect of impurities on the molecular weight of the product polymers was accounted for using a simple model.

A morphology diagram was developed to determine the range in composition and molecular weight over which this morphology existed. The degradability of the minor component, polylactide, along with the mild degradation chemistry allowed for the formation of a voided structure without disturbing the remaining porous polystyrene framework.

A new type of silica-based stationary phase with dramatically improved acid stability compared to any currently available silica-based stationary phase has been developed. Superior low pH stability is achieved by first self-assembling a densely bonded monolayer of (chloromethyl)-phenylethyltrichlorosilane (CMPES). The self-assembly step is followed by a Friedel--Crafts cross-linking of the reactive moieties with their neighbors, by addition of secondary, cross-linkable aromatic reagents, or by both. This phase is not endcapped. Elemental analysis data shows that an aluminum chloride catalyst is very effective at bonding aromatic cross-linking reagents, such as styrene heptamer and triphenylmethane, to the reactive CMPES monolayer. The stability of the retention factor of decylbenzene on the cross-linked self-assembled CMPES phases is compared to a sterically protected [C.sub.18] phase to illustrate its superior resistance to acid-catalyzed-phase loss. Inverse size exclusion chromatography and flow-curve comparisons of the cross-linked self-assembled CMPES and the sterically protected [C.sub.18] stationary phases illustrate their similar chromatographic efficiency.

Research has been conducted on the cyclic esters' ring-opening polymerization. The structural characterization of the iron(III)-alkoxide complexes and the comparative studies of the compounds' behavior have been carried out and are described.